Field of the Invention
This invention relates to non-volatile memory (NVM) systems and, more particularly, to controlling access to NVM systems.
Description of the Related Art
In a typical processing application (e.g., an automotive application) a non-volatile memory (NVM) may be implemented in a stand-alone memory integrated circuit or may be embedded within other integrated circuits. The NVM is used to store information, such as boot instructions, configuration information (e.g., operational parameters or information related to security and access), and/or other types of information, that are accessed and used by a microcontroller or other processing circuit to perform various operations. To protect the confidentiality and/or integrity of that information, e.g., to prevent unauthorized software execution or attack by malware, a manufacturer may use a cryptographic key to encrypt and/or control access to the information stored in the NVM of a product. The information is inaccessible unless a user (e.g., a microcontroller or other control circuit of the associated system) provides the cryptographic key to a memory access controller. The user uses the same cryptographic key to decrypt the information and/or secure access to the information from the NVM. The cryptographic key is stored in a non-volatile, read-only permanent key register. However, if secrecy of the cryptographic key is compromised, the system is vulnerable to attack. To change the cryptographic key requires that the system be returned to the manufacturer for device replacement. Accordingly, improved techniques for controlling access to information are desired.
The use of the same reference symbols in different drawings indicates similar or identical items.